Evaluating the effectiveness and reliability of the Vibrant Soundbridge and Bonebridge auditory implants in clinical practice: Study design and methods for a multi-centre longitudinal observational study.

BACKGROUND: The Vibrant Soundbridge middle ear implant and the Bonebridge bone conducting hearing device are hearing implants that use radio frequency transmission to send information from the sound processor to the internal transducer. This reduces the risk of skin problems and infection but requires a more involved surgical procedure than competitor skin penetrating devices. It is not known whether more complex surgery will lead to additional complications. There is little information available on the reliability of these systems and adverse medical or surgical events. The primary research question is to determine the reliability and complication rate for the Vibrant Soundbridge and Bonebridge. The secondary research question explores changes in quality of life following implantation of the devices. The tertiary research question looks at effectiveness via changes in auditory performance. METHOD: The study was designed based on a combination of a literature search, two clinician focus groups and expert review.A multi-centre longitudinal observational study was designed. There are three study groups, two will have been implanted prior to the start of the study and one group, the prospective group, will be implanted after initiation of the study. Outcomes are surgical questionnaires, measures of quality of life, user satisfaction and speech perception tests in quiet and in noise. CONCLUSION: This is the first multi-centre study to look at these interventions and includes follow up over time to understand effectiveness, reliability, quality of life and complications.

Cochlear implants for pre-lingually profoundly deaf adults.

INTRODUCTION: Increasing numbers of pre-lingually profoundly deaf adults are seeking a cochlear implant (CI). Pre- and post-operative outcomes are presented on 20 of these patients. RESULTS: An Adult Pre-Lingually Profoundly Deaf Implant Profile (APDIP) weighted the pre-operative level of concern about potential CI benefit. Results indicated no group mean post-operative open-set improvement. However CUNY sentence testing (auditory plus lip-reading cues) revealed improved performance with a CI. Twelve out of 20 patients used their CIs for more than 10 hours per day, suggesting good usage. Moreover, hours of usage were positively associated with measured benefit on CUNY sentences in the lip-reading plus sound via CI condition. There was no apparent relationship between pre-operative level of concern and post-operative CI performance or hours of processor use. CONCLUSION: Results suggest implantation is beneficial and effective in this group.

Assessment of 'Fitting to Outcomes Expert' FOX™ with new cochlear implant users in a multi-centre study.

OBJECTIVE: To compare the fitting time requirements and the efficiency in achieving improvements in speech perception during the first 6 months after initial stimulation of computer-assisted fitting with the Fitting to Outcome eXpert' (FOX) and a standard clinical fitting procedure. METHOD: Twenty-seven post-lingually deafened adults, newly implanted recipients of the Advanced Bionics HiRes 90K™ cochlear implant from Germany, the UK, and France took part in a controlled, randomized, clinical study. Speech perception was measured for all participants and fitting times were compared across groups programmed using FOX and conventional programming methods. RESULTS: The fitting time for FOX was significantly reduced at 14 days (P < 0.001) but equivalent over the 6-month period. The groups were not well matched for duration of deafness; therefore, speech perception could not be compared across groups. DISCUSSION: Despite including more objective measures of performance than a standard fitting approach and the adjustment of a greater range of parameters during initial fitting, FOX did not add to the overall fitting time when compared to the conventional approach. FOX significantly reduced the fitting time in the first 2 weeks and by providing a standard fitting protocol, reduced variability across centres. CONCLUSIONS: FOX computer-assisted fitting can be successfully used at switch on, in different clinical environments, reducing fitting time in the first 2 weeks and is efficient at providing a usable program.

Benefits of the HiRes 120 coding strategy combined with the Harmony processor in an adult European multicentre study.

CONCLUSION: The Harmony processor was found to be reliable, comfortable and offered a substantially increased battery life compared with the previous generation processor. No significant improvement in speech understanding with HiRes was demonstrated from objective measures, but the majority of subjects showed a clear subjective preference for the combination HiRes 120/Harmony processor. OBJECTIVES: To evaluate experience with the Harmony™ sound processor, together with the HiRes 120 strategy. METHODS: Postlingually deafened adults implanted with a CII or HiRes 90K were included and divided into three groups: (1) experienced users using the Platinum body-worn processor; (2) experienced users who had been using other processors; (3) new users with the Harmony processor from first fitting. The latter group entered a randomized crossover protocol where half were initially fitted with HiRes and half with HiRes 120. The initial strategy was used for 3 months and the alternative for a further 3 months. Speech perception tests and questionnaires were performed. RESULTS: The study included 65 subjects. Implementing HiRes 120 was straightforward. The speech test group results did not show significant differences between HiRes and HiRes 120. However, the questionnaires showed significantly higher ratings for HiRes 120 in some instances. Subjects were highly satisfied with the Harmony processor.

Simultaneous grouping in cochlear implant listeners: can abrupt changes in level be used to segregate components from a complex tone?

A sudden increase in the amplitude of a component often causes its segregation from a complex tone, and shorter rise times enhance this effect. We explored whether this also occurs in implant listeners (n = 8). Condition 1 used a 3.5-s "complex tone" comprising concurrent stimulation on five electrodes distributed across the array of the Nucleus CI24 implant. For each listener, the baseline stimulus level on each electrode was set at 50% of the dynamic range (DR). Two 1-s increments of 12.5%, 25%, or 50% DR were introduced in succession on adjacent electrodes within the "inner" three of those activated. Both increments had rise and fall times of 30 and 970 ms or vice versa. Listeners reported which increment was higher in pitch. Some listeners performed above chance for all increment sizes, but only for 50% increments did all listeners perform above chance. No significant effect of rise time was found. Condition 2 replaced amplitude increments with decrements. Only three listeners performed above chance even for 50% decrements. One exceptional listener performed well for 50% decrements with fall and rise times of 970 and 30 ms but around chance for fall and rise times of 30 and 970 ms, indicating successful discrimination based on a sudden rise back to baseline stimulation. Overall, the results suggest that implant listeners can use amplitude changes against a constant background to pick out components from a complex, but generally these must be large compared with those required in normal hearing. For increments, performance depended mainly on above-baseline stimulation of the target electrodes, not rise time. With one exception, performance for decrements was typically very poor.

Speech perception after cochlear implantation in 53 patients with otosclerosis: multicentre results.

OBJECTIVES: To analyse the speech perception performance of 53 cochlear implant recipients with otosclerosis and to evaluate which factors influenced patient performance in this group. The factors included disease-related data such as demographics, pre-operative audiological characteristics, the results of CT scanning and device-related factors. METHODS: Data were reviewed on 53 patients with otosclerosis from 4 cochlear implant centres in the United Kingdom and the Netherlands. Comparison of demographics, pre-operative CT scans and audiological data revealed that the patients from the 4 different centres could be considered as one group. Speech perception scores had been obtained with the English AB monosyllable tests and Dutch NVA monosyllable tests. Based on the speech perception scores, the patients were classified as poor or good performers. The characteristics of these subgroups were compared. RESULTS: There was wide variability in the speech perception results. Similar patterns were seen in the phoneme scores and BKB sentence scores between the poor and good performers. The two groups did not differ in age at onset of hearing loss, duration of hearing loss, progression, age at onset of deafness, or duration of deafness. CONCLUSIONS: The clinical presentation of the otosclerosis (rapid or slow progression) did not influence speech perception. Better performance was related to less severe signs of otosclerosis on CT scan, full insertion of the electrode array, little or no facial nerve stimulation and little or no need to switch off electrodes.

Auditory stream segregation in cochlear implant listeners: measures based on temporal discrimination and interleaved melody recognition.

The evidence that cochlear implant listeners routinely experience stream segregation is limited and equivocal. Streaming in these listeners was explored using tone sequences matched to the center frequencies of the implant's 22 electrodes. Experiment 1 measured temporal discrimination for short (ABA triplet) and longer (12 AB cycles) sequences (tone/silence durations = 60/40 ms). Tone A stimulated electrode 11; tone B stimulated one of 14 electrodes. On each trial, one sequence remained isochronous, and tone B was delayed in the other; listeners had to identify the anisochronous interval. The delay was introduced in the second half of the longer sequences. Prior build-up of streaming should cause thresholds to rise more steeply with increasing electrode separation, but no interaction with sequence length was found. Experiment 2 required listeners to identify which of two target sequences was present when interleaved with distractors (tone/silence durations = 120/80 ms). Accuracy was high for isolated targets, but most listeners performed near chance when loudness-matched distractors were added, even when remote from the target. Only a substantial reduction in distractor level improved performance, and this effect did not interact with target-distractor separation. These results indicate that implantees often do not achieve stream segregation, even in relatively unchallenging tasks.

Auditory stream segregation of tone sequences in cochlear implant listeners.

Previous claims that auditory stream segregation occurs in cochlear implant listeners are based on limited evidence. In experiment 1, eight listeners heard tones presented in a 30-s repeating ABA-sequence, with frequencies matching the centre frequencies of the implant's 22 electrodes. Tone A always stimulated electrode 11 (centre of the array); tone B stimulated one of the others. Tone repetition times (TRTs) from 50 to 200 ms were used. Listeners reported when they heard one or two streams. The proportion of time that each sequence was reported as segregated was consistently greater with increased electrode separation. However, TRT had no significant effect, and the perceptual reversals typical of normal-hearing listeners rarely occurred. The results may reflect channel discrimination rather than stream segregation. In experiment 2, six listeners performed a pitch-ranking task using tone pairs (reference=electrode 11). Listeners reported which tone was higher in pitch (or brighter in timbre) and their confidence in the pitch judgement. Similarities were observed in the individual pattern of results for reported segregation and pitch discrimination. Many implant listeners may show little or no sign of automatic stream segregation owing to the reduced perceptual space within which sounds can differ from one another.

Medical and surgical complications of the second 100 adult cochlear implant patients in Birmingham.

One hundred consecutive adult cochlear implant patients, numbered 101 to 200 in an ongoing series, were prospectively monitored and data collected using the same protocol as for the first 100 patients. The study period was 1999 to 2001. The total number of procedures was 122. Changes in practice following the first 100 implants included a standard surgical technique with a smaller incision and lesser flap mobilization, and routine facial nerve monitoring. As far as was practicable, the same commercial type of implant was used. There were 111 (91 per cent) implantation episodes, five (4 per cent) explantation episodes, four (3.3 per cent) reimplantation episodes and two (1.6 per cent) revision procedures. Eighty-nine patients underwent unilateral implantation and 11 underwent bilateral implantation. Major complications included flap breakdown (1.6 per cent), extrusion of electrode array (0.8 per cent) and device failure (0.8 per cent). The overall major complication rate was 3.2 per cent (4/122). The overall minor complication rate was 18 per cent. In addition, 7.3 per cent experienced transient vertigo and 5.7 per cent experienced local discomfort lasting three days on average with complete resolution. The overall complication rate in the second 100 implant patients was lower than in the first 100. Smaller incision and lesser flap mobilization reduced the minor complication rate.

Explantation and reimplantation of cochlear implants.

This study looks at the rates of explantation and reimplantation surgery in adult cochlear implant patients between 1990 and 2002 and also evaluates the surgical and audiological implications. 15 (5.5%) out of 272 adult cochlear implantees (288 cochlear implants: 282 Nucleus, 4 MED-EL Combi 40, 2 Clarion) needed their devices removed (explanted). 14 out of the 15 patients selected received explantation, reimplantation or revision surgery. The main reasons included device failure (2.2%), wound and flap problems (1.8%), and electrode extrusion (0.73%). Wound and flap problems were more common with larger skin incisions. In staged reimplantations, reinsertion was made easier if the electrode was retained in situ until reimplantation. Performance of the replacement device was not related to the aetiology of deafness or to the cause of explantation. These data will be useful in counselling patients.

Patient satisfaction with bilateral bone-anchored hearing aids: the Birmingham experience.

The Birmingham bone-anchored hearing aid (BAHA) programme has fitted more than 300 patients with unilateral bone-anchored hearing aids since 1988. Some of the patients who benefited well with unilateral aids and who had used bilateral conventional aids previously applied for bilateral amplification. To date, 15 patients have been fitted with bilateral BAHAs. The benefits of bilateral amplification have been compared to unilateral amplification in 11 of these patients. Subjective analysis in the form of validated comprehensive questionnaires was undertaken. The Glasgow benefit inventory (GBI), which is a subjective patient orientated post-interventional questionnaire developed to evaluate any otorhinolaryngological surgery and therapy was administered. The results revealed that the use of bilateral bone-anchored hearing aids significantly enhanced general well being (patient benefit) and improved the patient's state of health (quality of life). The Chung and Stephens questionnaire which addresses specific issues related to binaural hearing was used. Our preliminary results are encouraging and are comparable to the experience of the Nijmegen BAHA group.

Speech intelligibility with bilateral bone-anchored hearing aids: the Birmingham experience.

The Birmingham bone-anchored hearing aid (BAHA) programme, since its inception in 1988, has fitted more than 300 patients with unilateral bone-anchored hearing aids. Recently, some of the patients who benefited extremely well with unilateral aids applied for bilateral amplification. To date, 15 patients have been fitted with bilateral BAHAs. The benefits of bilateral amplification have been compared to unilateral amplification in 11 of these patients who have used their second BAHA for 12 months or longer. Following a subjective analysis in the form of comprehensive questionnaires, objective testing was undertaken to assess specific issues such as 'speech recognition in quiet', 'speech recognition in noise' and a modified 'speech-in-simulated-party-noise' (Plomp) test. 'Speech in quiet' testing revealed a 100 per cent score with both unilateral and bilateral BAHAs. With 'speech in noise' all 11 patients scored marginally better with bilateral aids compared to best unilateral responses. The modified Plomp test demonstrated that bilateral BAHAs provided maximum flexibility when the origin of noise cannot be controlled as in day-to-day situations. In this small case series the results are positive and are comparable to the experience of the Nijmegen BAHA group.